Add tutorial embedded app (#772)

Add embedded app for LLM Tutorial: OpenAI, LangChain, and Streamlit in 18 lines of code

Author: sfc-gh-dmatthews

python/tutorial-source/llm-18-lines-of-code/requirements.txt

@@ -0,0 +1,3 @@
+streamlit
+openai
+langchain

python/tutorial-source/llm-18-lines-of-code/streamlit_app.py

@@ -0,0 +1,19 @@
+import streamlit as st
+from langchain.llms import OpenAI
+
+st.title('🦜🔗 Quickstart App')
+
+openai_api_key = st.sidebar.text_input('OpenAI API Key')
+
+def generate_response(input_text):
+  llm = OpenAI(temperature=0.7, openai_api_key=openai_api_key)
+  st.info(llm(input_text))
+
+with st.form('my_form'):
+  text = st.text_area('Enter text:', 'What are the three key pieces of advice for learning how to code?')
+  submitted = st.form_submit_button('Submit')
+  if not openai_api_key.startswith('sk-'):
+    st.warning('Please enter your OpenAI API key!', icon='⚠')
+  if submitted and openai_api_key.startswith('sk-'):
+    generate_response(text)
+